Parkinson's disease (also known as Parkinson disease, Parkinson's, idiopathic parkinsonism, primary parkinsonism, PD, or paralysis agitans) is a degenerative disorder of the central nervous system. It results from the death of dopamine-containing cells in the substantia nigra, a region of the midbrain; the cause of cell-death is unknown. Early in the course of the disease, the most obvious symptoms are movement- and balance-related, including shaking, rigidity, slowness of movement and difficulty with walking and gait. The main motor symptoms are collectively called parkinsonism, or a “parkinsonian syndrome”. The pathology of the disease is characterized by the accumulation of a protein called alpha-synuclein into inclusions called Lewy bodies in neurons, and from insufficient formation and activity of dopamine produced in certain neurons of parts of the midbrain.
Modern treatments try to manage the early motor symptoms of the disease, mainly through the use of levodopa and dopamine agonists. As the disease progresses and dopamine neurons continue to be lost, a point eventually arrives at which these drugs become ineffective at treating the symptoms and at the same time produce a complication called dyskinesia, marked by involuntary writhing movements. Therefore, there is a need in the art to treat motor symptoms in subjects with Parkinson's Disease, including symptoms of Parkinson's Disease as well as symptoms indirectly associated with Parkinson's Disease, such as those arising as side effects of treatment.